Academic journal article Canadian Journal of Experimental Psychology

Individual Differences in Working Memory, Secondary Memory, and Fluid Intelligence: Evidence from the Levels-of-Processing Span Task

Academic journal article Canadian Journal of Experimental Psychology

Individual Differences in Working Memory, Secondary Memory, and Fluid Intelligence: Evidence from the Levels-of-Processing Span Task

Article excerpt

Individual differences in working memory (WM) are related to performance on secondary memory (SM), and fluid intelligence (gF) tests. However, the source of the relation remains unclear, in part because few studies have controlled for the nature of encoding; therefore, it is unclear whether individual variation is due to encoding, maintenance, or retrieval processes. In the current study, participants performed a WM task (the levels-of-processing span task; Rose, Myerson, Roediger III, & Hale, 2010) and a SM test that tested for both targets and the distracting processing words from the initial WM task. Deeper levels of processing at encoding did not benefit WM, but did benefit subsequent SM, although the amount of benefit was smaller for those with lower WM spans. This result suggests that, despite encoding cues that facilitate retrieval from SM, low spans may have engaged in shallower, maintenance-focused processing to maintain the words in WM. Low spans also recalled fewer targets, more distractors, and more extralist intrusions than high spans, although this was partially due to low spans' poorer recall of targets, which resulted in a greater number of opportunities to commit recall errors. Delayed recall of intrusions and commission of source errors (labeling targets as processing words and vice versa) were significant negative predictors of gF. These results suggest that the ability to use source information to recall relevant information and withhold recall of irrelevant information is a critical source of both individual variation in WM and the relation between WM, SM, and gF.

Keywords: working memory, secondary memory, fluid intelligence, levels of processing

Individual differences in working memory (WM) are related to a wide variety of higher-order cognitive abilities, such as fluid intelligence (gF) (see Unsworth & Engle, 2007, for a review). For this reason, a great deal of research has been conducted in an attempt to understand performance on WM tasks. However, debate surrounds the specific sources of individual variation in WM and the relation between WM and gF (e.g., Mogle, Lovett, Stawski, & Sliwinski, 2008; Shelton, Elliott, Matthews, Hill, & Gouvier, 2010; Unsworth, Brewer, & Spillers, 2009).

According to Unsworth and Engle's (2007) dual-component framework of WM, individual differences in secondary memory (SM) retrieval underlie individual differences in performance on WM tasks and are responsible, in part, for the relation between WM and gF. Unsworth and Engle (2007) proposed that WM tasks (e.g., complex span tasks such as operation span) predict gF because they require retrieving items from SM when they have been displaced from primary memory (PM). According to their framework, controlled retrieval is the key ability that is common to measures of WM, SM, and gF.

Working Memory and Secondary Memory

Several lines of research support the notion that individual differences in performance on WM tasks are driven by differences in the ability to retrieve information from SM. For example, individuals with higher scores on WM span tasks ("high spans") outperform individuals with lower scores on WM span tasks ("low spans") and on SM tasks as well (e.g., Unsworth, 2007). This is particularly true for SM tasks that emphasize recollection over familiarity, such as local versus global recognition (Oberauer, 2005) or source recognition versus item recognition (Unsworth & Brewer, 2009).

Most studies examining variation in both WM and SM tasks have focused on differences in retrieval processes as the key source of individual differences. However, it is important to also consider the way in which encoding processes impact the nature of subsequent retrieval processes. To overcome this limitation, the current study examined the impact of an encoding manipulation on individual differences in WM and SM.

If low spans use poor retrieval cues to retrieve items from SM, would their recall benefit if they encoded better retrieval cues? …

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